
(function (name, factory) {
  if (typeof window === "object") {
    window[name] = factory();
  }
})
("Ribbons", function () {
  var _w = window, _b = document.body, _d = document.documentElement;

  //随机函数
  var random = function () {
    if (arguments.length === 1) {
      if (Array.isArray(arguments[0])) {
        var index = Math.round(random(0, arguments[0].length - 1));
        return arguments[0][index];
      }
      return random(0, arguments[0]);
    } else
    if (arguments.length === 2) {
      return Math.random() * (arguments[1] - arguments[0]) + arguments[0];
    }
    return 0;
  };

  //屏幕信息
  var screenInfo = function (e) {
    var width = Math.max(0, _w.innerWidth || _d.clientWidth || _b.clientWidth || 0),
        height = Math.max(0, _w.innerHeight || _d.clientHeight || _b.clientHeight || 0),
        scrollx = Math.max(0, _w.pageXOffset || _d.scrollLeft || _b.scrollLeft || 0) - (_d.clientLeft || 0),
        scrolly = Math.max(0, _w.pageYOffset || _d.scrollTop || _b.scrollTop || 0) - (_d.clientTop || 0);
    return {
      width: width,
      height: height,
      ratio: width / height,
      centerx: width / 2,
      centery: height / 2,
      scrollx: scrollx,
      scrolly: scrolly
    };
  };

  var mouseInfo = function (e) {
    var screen = screenInfo(e),
        mousex = e ? Math.max(0, e.pageX || e.clientX || 0) : 0,
        mousey = e ? Math.max(0, e.pageY || e.clientY || 0) : 0;

    return {
      mousex: mousex,
      mousey: mousey,
      centerx: mousex - screen.width / 2,
      centery: mousey - screen.height / 2
    };
  };

  //点
  var Point = function (x, y) {
    this.x = 0;
    this.y = 0;
    this.set(x, y);
  };
  //点运算
  Point.prototype = {
    constructor: Point,
    set: function (x, y) {
      this.x = x || 0; this.y = y || 0;
    },
    copy: function (point) {
      this.x = point.x || 0; this.y = point.y || 0; return this;
    },
    multiply: function (x, y) {
      this.x *= x || 1; this.y *= y || 1; return this;
    },
    divide: function (x, y) {
      this.x /= x || 1; this.y /= y || 1; return this;
    },
    add: function (x, y) {
      this.x += x || 0; this.y += y || 0; return this;
    },
    subtract: function (x, y) {
      this.x -= x || 0; this.y -= y || 0; return this;
    },
    clampX: function (min, max) {
      this.x = Math.max(min, Math.min(this.x, max)); return this;
    },
    clampY: function (min, max) {
      this.y = Math.max(min, Math.min(this.y, max)); return this;
    },
    flipX: function () {
      this.x *= -1; return this;
    },
    flipY: function () {
      this.y *= -1; return this;
    }
  };

  //丝带画板
  var Factory = function (options) {
    this._canvas = null;
    this._context = null;
    this._sto = null;
    this._width = 0;
    this._height = 0;
    this._scroll = 0;
    this._ribbons = [];
    this._options = {
      id: "bgCanvas",//画板Id
      backgroundColor: "#33363b",//画板背景
      colorSaturation: "80%",//纯度
      colorBrightness: "60%",//亮度
      colorAlpha: 0.65,//透明度
      colorCycleSpeed: 6,//丝带不同块之间的色彩变化量
      verticalPosition: "center",//丝带相对于屏幕的初始位置：top/min 屏幕最上方，middle|center 中间，bottom|max 屏幕最下面
      horizontalSpeed: 200,//丝带水平方向移动速度参数（会乘以一个随机值）
      ribbonCount: 3,//同一时间丝带总条数
      strokeSize: 0,//公共边路径样式
      parallaxAmount: -0.5,//滚动偏移参数，-1表示不偏移，0表示基于丝带只出现在页面最上面
      animateSections: true//丝带块是否偏移，显得有动感
    };
    this._onDraw = this._onDraw.bind(this);
    this._onResize = this._onResize.bind(this);
    this._onScroll = this._onScroll.bind(this);
    this.setOptions(options);
    this.init();
  };
  Factory.prototype = {
    constructor: Factory,
    setOptions: function (options) {
      if (typeof options === "object") {
        for (var key in options) {
          if (options.hasOwnProperty(key)) {
            this._options[key] = options[key];
          }
        }
      }
    },
    //初始化
    init: function () {
      //初始化画板
      try {
        this._canvas = document.createElement("canvas");
        this._canvas.style["display"] = "block";
        this._canvas.style["position"] = "fixed";
        this._canvas.style["margin"] = "0";
        this._canvas.style["padding"] = "0";
        this._canvas.style["border"] = "0";
        this._canvas.style["outline"] = "0";
        this._canvas.style["left"] = "0";
        this._canvas.style["top"] = "0";
        this._canvas.style["width"] = "100%";
        this._canvas.style["height"] = "100%";
        this._canvas.style["z-index"] = "-1";
        this._canvas.style["background-color"] = this._options.backgroundColor;
        this._canvas.id = this._options.id;
        this._onResize();
        this._context = this._canvas.getContext("2d");
        this._context.clearRect(0, 0, this._width, this._height);
        this._context.globalAlpha = this._options.colorAlpha;
        window.addEventListener("resize", this._onResize);
        window.addEventListener("scroll", this._onScroll);
        document.body.appendChild(this._canvas);
      }
      catch (e) {
        console.warn("Canvas Context Error: " + e.toString());
        return;
      }
      //开始绘画
      this._onDraw();
    },
    //生成一条丝带
    addRibbon: function () {
      var dir = Math.round(random(1, 9)) > 5 ? "right" : "left",//丝带延伸方向
          stop = 1000,
          hide = 200,
          min = 0 - hide,
          max = this._width + hide,
          movex = 0,
          movey = 0,
          startx = dir === "right" ? min : max,//起始点x左边
          starty = Math.round(random(0, this._height));//起始点y左边

      //丝带生成的位置
      if (/^(top|min)$/i.test(this._options.verticalPosition)) {//最上方
        starty = 0 + hide;
      } else if (/^(middle|center)$/i.test(this._options.verticalPosition)) {//中间
        starty = this._height / 2;
      } else if (/^(bottom|max)$/i.test(this._options.verticalPosition)) {//最下方
        starty = this._height - hide;
      }

      if (this._options.parallaxAmount !== 0) {
        starty += this._scroll;//加上滚动
      }

      var ribbon = [],
          point1 = new Point(startx, starty),
          point2 = new Point(startx, starty),
          point3 = null,
          color = Math.round(random(0, 360)),
          delay = 0;

      //从起始位置开始生成一条丝带
      //丝带每个分部都是一个三角形，三点确定一个三角形，相邻三角形有一条公共边
      while (true) {
        if (stop <= 0) break;
        stop--;
        movex = Math.round((Math.random() * 1 - 0.2) * this._options.horizontalSpeed);
        movey = Math.round((Math.random() * 1 - 0.5) * (this._height * 0.25));
        point3 = new Point();
        point3.copy(point2);
        if (dir === "right") {
          point3.add(movex, movey);
          if (point2.x >= max) break;
        } else if (dir === "left") {
          point3.subtract(movex, movey);
          if (point2.x <= min) break;
        }
        ribbon.push({
          //三点
          point1: new Point(point1.x, point1.y),
          point2: new Point(point2.x, point2.y),
          point3: point3,
          color: color,//丝带颜色
          delay: delay,//延迟消失
          dir: dir,//方向
          alpha: 0,//透明度
          phase: 0 //随机位移有关参数
        });
        //公共边
        point1.copy(point2);
        point2.copy(point3);
        delay += 4;
        color += this._options.colorCycleSpeed;
      }
      this._ribbons.push(ribbon);
    },
    //绘制一个三角形方块
    _drawRibbonSection: function (section) {
      if (section) {
        if (section.phase >= 1 && section.alpha <= 0) {
          return true;
        }
        if (section.delay <= 0) {
          section.phase += 0.02;
          section.alpha = Math.sin(section.phase) * 1;
          section.alpha = section.alpha <= 0 ? 0 : section.alpha;
          section.alpha = section.alpha >= 1 ? 1 : section.alpha;
          if (this._options.animateSections) {
            var mod = Math.sin(1 + section.phase * Math.PI / 2) * 0.1;
            if (section.dir === "right") {
              section.point1.add(mod, 0);
              section.point2.add(mod, 0);
              section.point3.add(mod, 0);
            } else {
              section.point1.subtract(mod, 0);
              section.point2.subtract(mod, 0);
              section.point3.subtract(mod, 0);
            }
            section.point1.add(0, mod);
            section.point2.add(0, mod);
            section.point3.add(0, mod);
          }
        } else {
          section.delay -= 0.5;
        }
        var s = this._options.colorSaturation,
            l = this._options.colorBrightness,
            c = "hsla(" + section.color + ", " + s + ", " + l + ", " + section.alpha + " )";

        //绘制一个方块
        this._context.save();
        if (this._options.parallaxAmount !== 0) {
          this._context.translate(0, this._scroll * this._options.parallaxAmount);
        }
        this._context.beginPath();
        this._context.moveTo(section.point1.x, section.point1.y);
        this._context.lineTo(section.point2.x, section.point2.y);
        this._context.lineTo(section.point3.x, section.point3.y);
        this._context.fillStyle = c;
        this._context.fill();
        if (this._options.strokeSize > 0) {
          this._context.lineWidth = this._options.strokeSize;
          this._context.strokeStyle = c;
          this._context.lineCap = "round";
          this._context.stroke();
        }
        this._context.restore();
      }
      return false;
    },
    //绘制丝带
    _onDraw: function () {
      //清空已经绘制过的丝带
      for (var i = 0, t = this._ribbons.length; i < t; ++i) {
        if (!this._ribbons[i]) {
          this._ribbons.splice(i, 1);
        }
      }
      this._context.clearRect(0, 0, this._width, this._height);//清空画板
      for (var a = 0; a < this._ribbons.length; ++a) {
        var ribbon = this._ribbons[a],
            numSections = ribbon ? ribbon.length : 0,
            numDone = 0;

        //绘制整条丝带
        for (var b = 0; b < numSections; ++b) {
          if (this._drawRibbonSection(ribbon[b])) {
            numDone++;
          }
        }
        //丝带已经全部飘过屏幕，设置为null,函数前面会自动清理
        if (numDone >= numSections) {
          this._ribbons[a] = null;
        }
      }
      //随机生成一条丝带
      if (this._ribbons.length < this._options.ribbonCount && Math.random() > 0.99) {
        this.addRibbon();
      }

      //调度交给系统，当需要刷新画板时调用指定的回调函数，用于提高性能
      requestAnimationFrame(this._onDraw);
    },
    //重新设置窗体大小时需要获取窗体大小
    _onResize: function (e) {
      var screen = screenInfo(e);
      this._width = screen.width;
      this._height = screen.height;
      if (this._canvas) {
        this._canvas.width = this._width;
        this._canvas.height = this._height;
        if (this._context) {
          this._context.globalAlpha = this._options.colorAlpha;
        }
      }
    },
    //滚动时获取滚动距离
    _onScroll: function (e) {
      var screen = screenInfo(e);
      this._scroll = screen.scrolly;
    }
  }; return Factory;
});

//初始化并绘制
new Ribbons({
  ribbonCount: 10,
  parallaxAmount: -0.99,

});